The present invention relates to a heat treatment system using superheated steam. In particular, the invention relates to a heat treatment system for producing carbides by carbonizing wooden or bamboo materials and for obtaining pyroligneous acid or bamboo vinegar, and for carrying out heat treatment of combustible waste materials, drying treatment of perishable refuse, for carrying out treatment for cooking of foods, thawing of frozen food, and treatment for sterilizing treatment of various types of products including foodstuffs.
As a heat treatment system using superheated steam known in the past, a system disclosed, for instance, in JPA-2001-115167 is known. This system comprises superheated steam generating means, a sealable type dry distillation oven, a container with free ventilation for accommodating raw materials such as wooden or bamboo materials, a spray nozzle for spraying the superheated steam to the materials in the container, cooling and collecting means for collecting dry-distilled vinegar from the gas, containing thermally decomposed products generated from the dry distillation oven, and a chimney for discharging the gas from inside. In this heat treatment system, the gas generated from wooden or bamboo materials by spraying of the superheated steam is maintained at a predetermined temperature until effective thermal decomposition products are generated while the materials are enclosed in the dry distillation oven, and the cooling and collecting means after confirming the generation of the effective thermal decomposition products.
In the conventional type heat treatment system as described above, only one type of steam superheating unit is provided in the superheated steam generating means. Thus, the temperature of the steam cannot be increased beyond a certain limit. As a result, this system cannot be used for a temperature treatment such as a dry and carbonizing treatment performed in the temperature range of 400-600° C., for an activation treatment in the temperature range of 900-1100° C., or for a graphitization treatment performed in the temperature range of 1500-2300° C. Also, the gas discharged from a chimney contains thermal decomposition products and this gives harmful effects to the environment.